1. Field of the Invention
The present invention relates to a vehicle navigation server.
2. Description of the Related Art
In recently developed vehicle navigation servers, a route to the destination of a vehicle is searched for based on data of the destination defined and input by a passenger, and data of the determined route and information relating to the route are sent to a vehicle navigation device built into the vehicle.
Japanese Patent No. 3288565 discloses a technique in which traffic regulation information, which is effective at present, is selected from data of traffic regulation information input from an external device, and the selected information is displayed on a map indicated by map display means.
However, the capacity of a memory built in the vehicle navigation device is limited; thus, if all data of the determined route and information related to the route are received, a heavy burden is imposed on the memory, which is not preferable.
Additionally, in the above patent, it is determined whether the traffic information is effective at present according to temporal selection of information; however, no geographical factor is considered in the determination. Even traffic information assigned to the determined route may not be very important if the traffic information relates to a point far from the vehicle. Accordingly, the technique disclosed in the patent is not always efficient.
In consideration of the above circumstances, an object of the present invention is to provide a vehicle navigation server for providing traffic information, which is useful and has a suitable data amount, to a vehicle navigation device, so as to make the vehicle have a comfortable travel.
Therefore, the present invention provides a vehicle navigation server (e.g., a navigation server 5 in an embodiment explained below) comprising:
a travel route calculating device for calculating at least one proposed travel route of a vehicle (e.g., a vehicle 3 in the embodiment) based on data input by a registrant to the server, the data including a current or start position and a destination of the vehicle;
a map mesh defining device for defining a map mesh consisting of mesh units (e.g., mesh units M01, M02 . . . , M08 in the embodiment), which contains the proposed travel route;
a traffic information extracting device for extracting traffic information relating to each mesh unit of the proposed travel route from a traffic information storage device (e.g., a storage device 16 in the embodiment) in turn, in a manner such that traffic information relating to the mesh unit which includes the start or current position of the vehicle (e.g., the mesh unit M01 in the embodiment) is obtained first;
a data amount monitoring device for monitoring a total amount of extracted information, where the data amount monitoring device terminates information extraction for the following mesh units when the total amount becomes equal to or larger than a predetermined value; and
a data sending device for sending the extracted traffic information to a vehicle navigation device (e.g., a vehicle navigation device 8 in the embodiment) built into the vehicle.
Typically, the traffic information is extracted for each mesh unit in order from the mesh unit closest to the vehicle to the mesh unit furthest from the vehicle.
According to the above structure, the traffic information sent to the vehicle navigation device is obtained in a manner such that the traffic information relating to each mesh unit is obtained in turn, from the first mesh unit which is closest to the vehicle. Therefore, useful information for the vehicle can be obtained, and such information is used for calculating a travel route, so that the vehicle can have a comfortable travel.
In addition, when the total amount of the obtained traffic information becomes equal to or larger than a predetermined value, no traffic information is further obtained for the following mesh units. Therefore, it is possible to prevent excessive burden from being imposed on the memory of the vehicle navigation device. That is, no traffic information relating to the mesh units, which follow the mesh unit at which the total amount of the obtained traffic information has become equal to or larger than a predetermined value, is obtained. Therefore, the area for which the traffic information is updated can be localized. In comparison with the case of obtaining the traffic information relating to all mesh units, the amount of transmitted data can be reduced, thereby reducing the cost and time necessary for communication. In addition, the obtained traffic information can be quickly reflected in map data, thereby improving the responsiveness. Here, the traffic information may be sent to the vehicle navigation device every time the traffic information for a mesh unit is obtained, or after the traffic information for all target mesh units (i.e., selected mesh units for which traffic information should be obtained) are obtained.
As a preferable example, the traffic information sent to the vehicle navigation device is selectable for each of information categories (e.g., traffic regulation information and traffic jam information in the embodiment), and traffic information belonging to at least one information category which is selected freely or in advance (e.g., the traffic regulation information in the embodiment) is extracted and sent to the vehicle navigation device. The at least one information category may be selected in advance by a passenger of the vehicle.
According to this example, the traffic information required by a passenger can be selected; thus, the traffic information which is essential for the passenger can be sent. Therefore, in comparison with the case of sending traffic information in all categories, the amount of the traffic information can be reduced, thereby further reducing the burden imposed on the memory of the vehicle navigation device.
As another preferable example, the traffic information sent to the vehicle navigation device is a combination of detailed information about a section (e.g., a section from mesh unit M01 to mesh unit M03 in the embodiment) from the mesh unit which includes the current or start position of the vehicle to a predetermined one of the mesh units (e.g., the mesh unit M03 in the embodiment) and simplified information about the remaining mesh units following the predetermined mesh unit.
According to this example, traffic information for a section relatively close to the vehicle, which (the information) is highly urgent or useful for a passenger of the vehicle, can be detailed information, while traffic information for a section relatively far from the vehicle can be simplified but highly-useful information. That is, only traffic information having high priority with respect to the necessity for the passenger can be sent. When receiving such traffic information, the vehicle navigation device can calculate a further suitable travel route, thereby further improving the comfort of travel of the vehicle.